#include <iostream>
#include <cstdlib>
#include <vector>
#include <cmath>

using namespace std;

// task1

void findRoot(double val, double &res1, double &res2, double &res3) {
    if (val < 0) {
        res1 = res2 = res3 = -1;
        return;
    }
    res1 = pow(val, 1.0/2);
    res2 = pow(val, 1.0/3);
    res3 = pow(val, 1.0/4);
}

void task1()
{
    double val;
    double res1, res2, res3;
    cout << "Input val:" << endl;
    cin >> val;

    findRoot(val, res1, res2, res3);
    cout << val << " " << res1 << " " << res2 << " " << res3 << endl;
}

// task2

int power(int n, int k) {
  if (k == 0)
    return 1;
  else if (k % 2)
    return n * power(n, k - 1);
  else
    return power(n * n, k / 2);
}

void task2() {
  int n, k;

  cout << "Input n: "; cin >> n;
  cout << "Input k: "; cin >> k;

  if (k < 0)
    cout << "k < 0";
  else
    cout << "n^k = " << power(n, k);

  cout << endl;
}

// task4

double eval(const string &str, const vector<double> &args) {
  double acc = 0, x;
  int arg = 0;
  enum { ADD, SUB, MUL, DIV, NOP, ERR } op = NOP;

  for (int i = 0; i < str.size(); i++) {
    switch (str[i]) {
    case 'i': case 'd':
      if (arg >= args.size()) {
        cout << "Need more args";
        exit(1);
      }

      x = args[arg++];

      switch (op) {
      case ADD: acc += x; break;
      case SUB: acc -= x; break;
      case MUL: acc *= x; break;
      case DIV: acc /= x; break;
      case NOP: acc =  x; break;
      case ERR: cout << "Syntax error";
                exit(1); }

      op = ERR; break;

    case '+': op = ADD; break;
    case '-': op = SUB; break;
    case '/': op = DIV; break;
    case '*': op = MUL; break;
    default : op = ERR; }
  }

  return acc;
}

void task4() {
  string expr, line;
  vector<double> args;

  cout << "Input expr: "; getline(cin, expr);
  cout << "Input args: ";
  while (getline(cin, line), !line.empty())
    args.push_back( atof(line.c_str()) );

  cout << "Result: " << eval(expr, args) << endl;
}

// task5

template <typename T>
const T& max_(const T &a, const T &b) {
  return a > b ? a : b;
}

template <typename T>
const T& max_(const T &a, const T &b, const T &c) {
  return max(max(a, b), c);
}

void task5() {
  int a, b, c;

  cout << "Input a: "; cin >> a;
  cout << "Input b: "; cin >> b;
  cout << "Input c: "; cin >> c;

  cout << "Max: " << max_(a, b, c);
}

int main() {
    int i;

    do {
      cout << "Input task number (1-5):" << endl;
      cin >> i;
      switch(i) {
      case 1:
        task1(); break;
      case 2:
        task2(); break;
      case 3:
        //task3(); break;
      case 4:
        task4(); break;
      case 5:
        task5(); break;
      case 0:
        cout << "Program is done" << endl; break;
      default:
        cout << "Invalid option" << endl; }
    } while(i != 0);

    return 0;
}